This invention concerns an apparatus for noncontact measurement of the position of a first member in relation to a second, ferromagnetic member in a direction tangent to the surface separating them, through said surface and independently of variations in position in a direction normal to said surface.
In particular, the first member is linked to a railway vehicle axle and the second member is one of the rails of the track on which the wheelset of this axle is running, the measurement being transverse to the axis of the track. It is notable that in this case, due to track intersections and turnouts, switch gear, grade crossings and the like, it is difficult to place a sensor below the plane of the running surface and that high speed travel requires a noncontacting sensor.
With a pair of these apparatus, in front of and behind a wheel of the axle, data can be had about the transverse and angular position of the axle in relation to the track, making it possible to make steerable trucks, ie. trucks (bogies) with steerable axle sets.